Motor vehicles, such as cars, marine vessels, trucks and the like almost universally include a battery that is used for engine ignition. The battery is also electrically connected to other electrical loads in the vehicle, such as hazard lights, radios, running lights, etc. Typically, a generator or alternator, driven by the engine, provides an electrical current for recharging the battery.
Oftentimes, the engine is shutoff and the battery continues to drive an electrical load in the vehicle and, in doing so, discharges the battery. In some cases, this can be inadvertent, such as leaving the headlights on, leaving the radio on, leaving the ignition keys in the accessory or on position, or through a malfunction in the electrical circuit. In any event and after a period of time, the battery will discharge to such an extent that engine cranking using the charge in the battery is impossible.
Accordingly, and in order to maintain a minimal threshold charge value in an automotive battery, it would be desirable to have a battery protection system which would disconnect the battery from an electrical load or draw, if the battery discharges below a set value. In addition, the system would need to distinguish the current status of the automobile (i.e. engine running) and the type of electrical systems being driven by the battery (i.e. hazard lights) in order to provide the system with a "fail-safe" protection system so that the battery is not disconnected from driving critical systems.
Moreover, the system will also be required to determine when to reconnect the battery in order to drive such systems.
In connecting a battery to a supply of D.C. power of the same voltage rating such as a battery charger, the battery and supply must be connected with their polarities matched. If the polarities are mismatched, a high-current condition might occur. The results will be possible damage to the battery or damage to the electrical components of the vehicle.
A similar situation may occur when a motorist attempts to "jump start" a vehicle having a dead battery, by using jumper cables to connect the dead battery to a vehicle having a fully charged battery. It is important that the positive terminal of the first battery be connected to the positive terminal of the second battery, and likewise for the negative terminals. However, it is not always possible to guarantee correct polarity matching. In a first situation, an unsophisticated motorist may not know how to properly connect the jumper cables. In a second situation, it may be difficult to determine the polarities of the batteries. This latter situation can occur when the polarity indicating indicia on the batteries is covered with oil and dirt, at night when the indicia is difficult to read, or in the haste and frustration that arises from attempting to jump start a car during extremely adverse weather conditions. Even under ideal circumstances, errors in matching polarities can still occasionally occur due to simple oversight.
In those instances in which polarities are mismatched during an attempt to start a stranded car, not only can the error cause damage to both vehicle electrical systems, but such damage may result in both vehicles becoming disabled in a remote location. For these reasons, it is highly desirable to prevent mismatching of battery polarities when a motorist is attempting to jump-start a stranded vehicle.
Accordingly, there is a need for a battery protection system that prevents the damage to the battery from short circuits or improper jump-start conditions. In addition, there is also a need for a battery protection system wherein the battery maintains a minimal charge for operating essential systems, such as the starter motor of an automobile.